Propellent charge for jet-propelled devices



Patented June 23, 1953 1 UNITED NT OFFICE.

PROPELLENT CHARGE FOR J ET-PROPELLED DEVICES No Drawing. Application January 15, 1944, Serial No. 518,457

7 6 Claims. ((11. 52 .5)

powder for use in conventional guns. This overall burning rate is in part reduced by producing the propellant charge in the form of relatively large grains of relatively thick web. These large grains because of their relatively low surfaceto-volume ratio exhibit an overall burning rate considerably less than that of the same or similar powder having grains of the size used in the production of conventional powders for con- 'ventional guns. Moreover, while it has long been recognized in the manufacture of conventional powders that the burning rate may be altered or retarded by the application of a coating composition to the surface of thhe powder grains, such a surface coating alters or retards the initial rate of burning of the grain without re- 'stricting the burning area of the grain and,

therefore, permits burning at too high a rate for satisfactory use of the coated grains in certain jet-propelled devices.

Now, in accordance with this invention, it

has been found that a coating composition consisting of lacquers containing chlorinated rubber applied on a part of the surface of a large smokeless powder grain will restrict the burning area of the grain and thereby still further reduce the overall burning rate of the grain, thereby rendering it suitable as a propellant charge for a jet-propelled device.

These lacquers are composed of chlorinated rubber, plasticizer, pigment, solvent, and resinous material. Table I shows preferred formulae for lacquers which have been found suitable as a flame-resistant coating composition for large smokeless powder grains:

Table I Formula No 1 2 3 4 5 6 Chlorinated rubber 15 15 l5 l5 Nickclous oxa1ate Tricresyl phosphate Ethyl acetate Lewisol F-103 l0 Percent by weight 100 100 100 100 100 100 With reference to Table I, the chlorinated rubber should have a chlorine content from about 65 to about 70% by weight. The viscosity of the chlorinated rubber may be in the range from about 10 centipoises to about 5000 centipoises (as determined at 25 C. in a capillary viscometer using a toluene solution containing by weight of chlorinated rubber), with a preferred range from about 20 centipoises to about 125 centipoises. The plasticizer may be dibutyl phthalate, tricresyl phosphate, diethyl phthalate, diamyl phthalate, triethyl citrate, Santicizer B-16 (butyl phthalyl butyl glycolate), or the like. The pigment may be manganous carbonate, naturally-occurring manganous carbonate (rhodochrosite), nickelous oxalate, calcium carbonate, zinc oxide, magnesium borate, or similar materials such as an oxide, a salt or the like which is substantialy nonvolatile at the combustion temperature of the smokeless powder or which may decompose at the combustion temperature of the smokeless powder to leave a substantially nonvolatile residue. The solvent may be a mixture of toluene and butyl acetate, a mixture of toluene and ethyl acetate, a mixture of Tollac (a hydrocarbon solvent containing a major portion of benzol by volume) and butyl acetate, a mixture of Tollac and ethyl acetate, or any similar organic solvent combination involving aliphatic or aromatic hydrocarbons, ketones, esters, chlorinated hydrocarbons, and the like. The resinous material may be a resin or resin-like material such as Rezyl 869 (drying oil glycerol phthalate alkyd) or Lewisol E -103 (drying oil glycerol phthalate alkyd) or any similar material such as a dryingoil-modified phthalate alkyd resin or a dryingoil-modified alkyd resin. Other materials may also be used as the resinous component in the present lacquer combinations such as natural resins and synthetic resins such as phenolformaldehyde and other resin-type materials which are compatible with chlorinated rubber.

The preferred proportions, in parts by weight, of the various constituents given above which can be used in the lacquers of the present invention are substantially those given in Table I above. However, it has been foundthat from about 5 to about parts of chlorinated rubber, from about 3 to about 10 parts of plasticizer, from about 20 to about 40 parts of pigment, from about 5 to about 20 parts of resin, and a solvent in proportion to form from about 30 to about 95% of the finished lacquer may be used. A solvent mixture of toluene or similar solvent with butyl or ethyl acetate may be used, said solvent mixture comprising from about 30 toabout 95% by weight of the lacquer ready for application to the powder, the toluene or similar solvent, and the butyl or ethyl acetate each comprising from about 10 to about of the lacquer ready for application to the powder.

The lacquers which have been found to be been found suitable.

suitable in accordance with this invention actually restrict the burning area of smokeless powder as shown in static firing tests carried out with the aid of rocket-type chambers provided with an opening at one end to allow escape of the gases formed by the burning ofthe powder. For a given powder, the pressure attained in such a chamber depends upon the ratio of the area of powder surface available for burning to the area of the opening which allows escape of the gases of combustion. Large grains of powder in the form of solid cylindrical sticks of powder were partially coated with lacquer, leaving one end not lacquered. The chambers were provided with a shear dis-c designed to be blown out when the pressure rose as high as or somewhat higher than about 5000 pounds per square inch. The pressure produced inside the chamber was measured by a copper ball pressure gage fitted in the side of the chamber. The results of Table II show that the burning pressure is lowered and the burning time is increased and hence that the burning surface is restricted by use of the lacquer. Typical results are shown The burning time for the unlacquered grain of powder in the above table was in the order of 0.1 second. The burning time for the lacquered grains of powder in the above table was in the order of several seconds.

The dry film thickness of the lacquer coating may be varied by the number of applications, the per cent solids of the lacquer andchoice of lacquer ingredients suchas plasticizers, resins, solvents, and viscosity-type of chlorinated rubber used. Applications of the lacquer as thin as 0.004 inch and as thick as 0.020 inch have The optimum thickness will be determined by the dimensions and burning characteristics of the powder grain, and the length of time for which burning is to be restricted.

The lacquers of the present invention may be applied to a powder consisting of any of a variety of compositions and to'powders both with and without nitroglycerin as a component. 7

With reference to Table II, it will be seen that when the lacquers of the present invention were applied to the surface or superficial part of a grain of smokeless powder, the maximum pressure was reduced and the burning time was increased. -When a proper means of ignition is applied to a powder grain so coated under conditions suitable for burning the powder at relatively low pressures, such as are met in jetpropelled devices, ignition of the powder grain will occur only on the unlacquered part of the surface or superficial portion of the grain. Under such conditions, burning proceeds fromthe ignited part of the surface or superficial portion inward into the body of the grain. .The part of the grain beneath the lacquered surface ultimately burns, but only as a result of the burning having progressed to it from a portion of the grain other than the lacquered surface.

The utility of the lacquers of the present invention resides principally in their use as a coating composition for large smokeless powder grains which are to be used as a source of energy in jet-propelled devices, such as rockets, airplane starters, assisted take-off devices, and the like, including any device which derives translational or rotational energy at least partly from the reaction producedfrom the issuance at relatively high speed of fluid medium from an opening in the device.

The lacquers of the present invention are easily and quickly applied to powder grains; they may be applied at room temperature without the inconvenience and danger which accompany the use of heated melts; they may be applied by simple means, such as dipping, brush- 'ing, or spraying; and require no time-consuming,

difficult operations or special equipment for their application.

WhatI claim and desire to protect by Letters Patent is:

1. As a new article of manufacture, a propel lant charge for a jet-propelled device which comprises a solid stick of smokeless powder and a flame-resistant film partially covering the surface of the solid stick, said flame-resistant film being formed from a composition comprising by weight from about to about 25 part of chlorinated rubber, from about 3 to about parts of a plasticizer, from about to about 40 parts of a pigment which is substantially nonvolatile at th combustion temperature of the smokeless.

' powder, from about 5 to about 20 parts of a resinous material compatible with the chlorinated rubber, and a solvent, said solvent being present in amount from about 30 to about by .weight of the composition ready for application to the stick of smokeless powder.

2. As a new article of manufacture, a propellant charge according to claim 1 wherein the pigment is manganous carbonate.

3. As a new article of manufacture, a propellant charge according to claim 1 wherein the lent charge for a jet-propelled device which comprises a solid stick of smokeless powder hav ing its surface partially covered with a coating comprising from about 5 to about 25 parts of chlorinated rubber, from about 3 to about 10 parts of plasticizer, from about 20 to about 40 parts of pigment which leaves a residue of solid material even after heating to the combustion temperature of the smokeless powder, and from,

about 5 to about 20 parts of a resinous material compatible with the chlorinated rubber.

6. As a new article "of manufacture, a propellent charge for a jet-propelled device which comprises a solid stick of smokeless powder having its surface, except for one end, covered with a coating comprising from about 5 to about 25 parts of chlorinated rubber, from about 3 to about 10 parts of plasticizer, from about 20 to about 40 parts of pigment which leavesa residue of solid material even after heating to the combustion temperature of the smokeless powder, and from about 5 to about 20 part of a resinous material compatible with the chlorinated rubber.

7 ROBERT W. CAIRNS.

(References on following page) 5 6 References Cited in the file of this patent Numbe Country Date UNITED STATES PATENTS 432,645 Great Britain July 31, 1935 Number Name Date 502,560 France Feb. 24:, 1920 846,522 Fran 12, 193 2,095,574 Roumazeilles Oct. 12, 1937 5 Ce June 9 2,145,539 Fander Jan. 31, 1939 OTHER REFERENCES 2,147,698 Goodyear Feb. 21, 1 39 Mattiello Protective & Decorative Coatings, 2,211,431 Olsen Aug. 13, 1940 vol. I, pages 467-470, 1941. 2,229,882 Binapfl Jan. 28, 1941 FOREIGN PATENTS 10 Number Country Date Great Britain Nov. 29, 1907 

1. AS A NEW ARTICLE OF MANUFACTURE, A PROPELLANT CHARGE FOR A JET-PROPELLED DEVICE WHICH COMPRISES A SOLID STICK OF SMOKELESS POWDER AND A FLAME-RESISTANT FLIM PARTIALLY COVERING THE SURFACE OF THE SOLID STICK, SAID FLAME-RESISTANT FILM BEING FORMED FROM A COMPOSITION COMPRISING BY WEIGHT FROM ABOUT 5 TO ABOUT 25 PARTS OF CHLORINATED RUBBER, FROM ABOUT 3 TO ABOUT 10 PARTS OF A PLASTICIZER, FROM ABOUT 20 TO ABOUT 40 PARTS OF A PIGMENT WHIHC IS SUBSTANTIALLY NONVOLATILE AT THE COMBUSTION TEMPERATURE OG THE SMOKELESS POWDER, FROM ABOUT 5 TO ABOUT 20 PARTS OF A RESINOUS MATERIAL COMPATIBLE WITH THE CHLORINATED RUBBER, AND A SOLVENT, SAID SOLVENT BEING PRESENT IN AMOUNT FROM ABOUT 30 TO ABOUT 95% BY WEIGHT OF THE COMPOSITION READY FOR APPLICATION TO THE STICK OF SMOKELESS POWDER. 